A biosafety cabinet (BSC) is an enclosed, ventilated laboratory workspace that allows laboratory workers to safely work with materials contaminated with (or potentially contaminated with) pathogens. The primary purpose of a biosafety cabinet is to protect laboratory workers and the surrounding environment from pathogens.
The U.S. Centers for Disease Control and Prevention (CDC) classifies biosafety cabinets into three classes. Most biosafety cabinets are a Class II, Type A2 cabinet. The principle of operation of these biosafety cabinets involves using a fan mounted in the top of a cabinet to draw a curtain of sterile air over the materials that are being handled. The air is circulated through a HEPA filter and then directed down underneath a work surface and back up to the top of the cabinet. A certain percentage of the air in the cabinet that is exhausted (after passing through the HEPA filter) is made up by air being drawn into the front of the cabinet underneath the workspace. The air being drawn into the work area acts as a barrier to potentially contaminated air coming back out to the operator. A Class II, Type A2 biosafety cabinet typically recirculates about 70% of the air used therein.
To ensure proper operation, the biosafety cabinet, particularly the HEPA filter, must be periodically cleaned and tested. Prior to servicing the biosafety cabinet, the enclosure must be decontaminated to protect service personnel from exposure to pathogens that may have been collected in the workspace of the cabinet or the filter.
A conventional method of decontaminating biosafety cabinets consists of sealing, i.e., closing, the opening to the workspace, and heating, i.e. boiling, formaldehyde within the enclosure. The formaldehyde vapors decontaminate the exposed surfaces of the workspace. A problem with this method of decontamination is that a residue is produced by the boiling of formaldehyde. The residue must be physically removed from the surfaces of the enclosure by a subsequent cleaning process. Moreover, it is difficult to decontaminate the HEPA filter using a formaldehyde process as described above. In this respect, when formaldehyde is used, a system blower is typically energized for a very short interval to draw some the vaporized formaldehyde into the filter. However, if the blower is allowed to operate too long, the aforementioned residue is collected within the HEPA filter and can clog the filter, thereby requiring its replacement. Too little exposure of the formaldehyde vapor can result in the filter not being completely decontaminated. Moreover, because the blower can be operated for only a relatively short period of time, the enclosure and the air passages downstream of the blower and the HEPA filter are not assuredly decontaminated.
The present invention overcomes this and other problems and provides a method and apparatus for decontaminating an enclosure, particularly a biosafety cabinet, that effectively and efficiently decontaminates the enclosure of a biosafety cabinet as well as the HEPA filter and lower passageways therein.